In this proposal we describe a research plan directed toward the obtention of several biologically active coriolin sesquiterpenes by means of chemical syntheses. The continuous supply of these compounds from natural sources in sufficient amounts for screening seems uncertain and therefore an efficient synthesis of the coriolins exhibiting antitumor and antibiotic properties is needed. Our synthetic plan thus focuses on the rapid production of a flexible tricyclic intermediate which is equipped with properly differentiated functionalities to permit its conversion into various coriolin natural products. This intermediate is accessible through the application of intramolecular cyclopentene annulation methodology which has been developed in our laboratory. The following features exemplify our plan: a. synthesis of four dienic diazoketones each of which differs in a single functionality at (what will become) the ring C of coriolins b. examination of three modes of ring closures of these diazoketones (thermal, acid catalyzed and metal-promoted) to produce a linear tricyclopentanoid. Special attention will be paid to the compatibility of the functional group at ring C with the methods of closure c. selection of the most efficient of these ring closures for a large scale production of the key tricyclo[6.3.0.(2,6)] undec-6-ene which is also functionalized at positions 2, 3, 10 and 11; and d. selective conversions of the above compound to five coriolins and three hirsutic acid type sesquiterpenes by bisepoxidative or alkylative operations respectively. The preliminary results regarding cyclopentene closures have been completed and accentuated with the total synthesis of hirsutene, the biogenetic presursor of coriolins in a high overall yield. The transformations dealing with the diverse functionalization of our intermediate have been well documented also. Our approach will furnish the coriolin sesquiterpenes stereo- and regio-selectively from a single, accessible intermediate. The overall merit of the proposed research would lie in the efficiency and the brevity of the outlined synthesis as compared to currently known preparations.